Mail failure - no recipient addresses

I have the Simplenews module (7.x-1.0-beta2) installed in my Drupal 7.12.

All function well, but after send one newsletter node to all subscribers I recive too much mails with this error:

A message that you sent contained no recipient addresses, and therefore no
delivery could be attempted.

------ This is a copy of your message, including all the headers. ------

To:
Subject: [Cursos i tallers] Curs d'autobiografia, Barcelona
MIME-Version: 1.0
Content-Type: multipart/mixed; boundary="dcb4c641cc11b46e591f06106ea2a24f"
Content-Transfer-Encoding: 8Bit
X-Mailer: Drupal
Sender: =?UTF-8?B?IlRyaXZpdW0gZ2VzdGnDsyBjdWx0dXJhbCIgPGluZm9AdHJpdml1bWdjLmNvbT4=?=
From: =?UTF-8?B?IlRyaXZpdW0gZ2VzdGnDsyBjdWx0dXJhbCIgPGluZm9AdHJpdml1bWdjLmNvbT4=?=
From: =?UTF-8?B?IlRyaXZpdW0gZ2VzdGnDsyBjdWx0dXJhbCIgPGluZm9AdHJpdml1bWdjLmNvbT4=?=@cpanel.creactivitat.com
Precedence: bulk
Message-Id:
Date: Thu, 19 Apr 2012 18:53:57 +0200

This is a multi-part message in MIME format.

--dcb4c641cc11b46e591f06106ea2a24f
Content-Type: multipart/related;
type="multipart/alternative";
boundary="5ce9242ef5c7a4d1481b76f0b0155fbb"
Content-Transfer-Encoding: 8bit

--5ce9242ef5c7a4d1481b76f0b0155fbb
Content-Type: multipart/alternative;
boundary="18241d8d3aa39dd46b82f998fb422265"
Content-Transfer-Encoding: 8bit

--18241d8d3aa39dd46b82f998fb422265
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
Content-Transfer-Encoding: 8bit

And the otiginal node code...

I can't understand this error because all the subscribers have your email address.
Some idea?